Allogeneic immunization is thought to be concerned with recurrent pregnancy loss. A unique immune system make it possible for fetal tissues that have paternal major histocompatibility complex to implant into the maternal uterus. According to the immunotrophism hypothesis that maternal inmunne recognize paternal antigen and promote placental growth, a shift in the Th1/Th2 balance toward Th2 is important in the immune system around decidua and placenta. Indoleamine 2,3-dioxygenase (IDO) that inhbit an increase of the cytetoxic T cell to produce Th1 cytekines is received attention. Flowcytemetry is useful for measurement of these cytokines.
